Method of producing tire molds



Sept. 16, 1930. I G. w. BUNGAY 1,776,145

METHOD OF PRODUCING TIRE HOLDS Filed May 6, 1929 2 Shoots-Shut l- Vi 5;: j; A 6 A a 5 15 7 J5 Z0 3 -32 L d 1 A0 if" l%////%//ir a 1Z /1Z I L ATTO NEY Sept. 16, 1930. G. w. BUNGAY I METHOD OF PRODUCING TIRE HOLDS Filed May 6, 1929 2 Shoa s-Shut 2 NVENTOR V 16 ,7 ATTORI umrso sTArssrA'rsNr oFFi-ce- GEORGE W. BUNGAY, OF rnmmm, In men, 816803 '10 flamenco! PANYOI OI MBYLVANIA, L

V mvama m0!) OI'PBODUCE'G rm HOLDS v a imate me m 0, me. semi It. seems.

, This invention relates to a methodof producing the molds' and more particularly to that class of molds which is used for mol ing treads on-rubber tires.

This application isa continuation in art of my :application Serial No. 281,654,

lication Serial No. 235,095, filed on Novemthe mold from steel and to engrave a pattern for the non-skid tread on the inside ofthe mold. This has been a very expensive process when repeated many times and particularly so, smce occasionallythe design would become injured when removing the finished tire from the mold by an iron-or crow-bar because of the adherence of the, rubber tread portion to the mold, and which. it was necesry to use in order to loosen the finished tire in the mold.

' Furthermore, with the steel molds now in use it is necessary to' sand-blast the interior of the mold frequently, generally after forty or. fifty tires have been made -in the same mold, in order to remove the-adhering articles of rubber called barnacles 'w 'ch tend to build up in the mold during the repeated operations.

' By my invention the necessity of cuttin a design in the mold is obviated, and I am a le to use the main portions of the mold indefinitely= and to renew the tread portion at will,

' whenever it is desired to change the, design or whenever the'desi becomes worn or in-'- jured. Also, in mol s, according tomy intional die-cast or -vention, thebarnacle-formin tendency is reduced to a minimum .anduent sandblasting is not required, as there is, practicall no adherence of the to the matrix,

t us permitting the molds f be used approx-- 'imatelytwo hundred and fifty times or more before cleaning is necessary. 5

All of the .above is accomplished by secaluminum alloy matrices of novel construction and the novel arran ement and methodby-which they are i assem led in the mold to provideammimum ofseams or pmt ed May 31, 1928, which is'a division of my-ap- Heretofore, the practice has been to make;

use steel molds with a desi the tire from the oonronanon or rgmm- Moreover, these matrices give the outside surfaceof the tire a very high polish and permit the tire to be stripped from the mold with far less difliculty than in the molds heretofore used. In addition, a sup ly 01Ev molds made after my invention may made from onefifth to one-tenth of the cost of the'molds'nowin-use, not necessary to only the injured be quickly replaced without di culty.

discard the entire mold but portion, which ortion may and in case of injury to the mold it is' I am aware that an attempt has been made to form the matrices for tire molds from castin 4 and to insert these matrices in the ,mold in sections, but-these attempts prior to my invention have been failures, so that i mold than from the all-steel 4 the sectional molds heretofore used than in the all-steel molds on account of the rubber adherin in the seams, crevices or to the ridges o the design, so that molds with sectional matrices have been heretofore worthless for any practical fpurpose.

Other objects and tion' will a pear from the following description and t e appended'claims;

'In the drawings whih ferredembodiment of my invention:

-Figure 1 shows a cross-section along diameter of the mold. v Figure 2 is aportion of Figure 1 enlarged.

Figure dis a side view of a section of my improved mold showing-the tire removed from the mold.

Figure 1s a plan view' of one of the mat-:

- "Fi in Figure 4.. J

Figure 6 is a sectibn'on line 66 of ure4. Q 4 f The'moldt whi'ch the present invention is illustrate the pre-,

the

gure 5 isa side'view of the matrixshown eatures of my inf enapplicablemay be of any suitable'or desirable ent disclosure it is shown as comprisin together.

enable the matrices to form a tread design factory results by subjecting the faces of the up to the parting line between the mold secconstruction, but for the purposes of the presan inner steel ring 1 0 the base 0 the mold and outer annular side sections 2 and 3 positioned on opposite sides of the ring 1, res an top of the mold cavity 4. The inner circumferential edges of the side sections 2 and 3 are formed with means complemental to means on the sides of the ring 1, as at 1', for maintaining the sections in 'tion when. the parts are secured together. The outer opposing edges of the sections 2 and 3 are formed with flanges 5 and 6 whichvoverlap when the mold sections 2 and 3 are brought These sections 2 and 3 are secured in position by a nut and bolt means 7 extending through outstanding flanges 8 and 9 upon the sections, respectively. a

The siderings of sections 2 and 3 are channeled or grooved as at 10 and 11, respectively, on their cavity-forming faces and at points thereof correspon to the tread portion of the tire. These c els or grooves 10 and 11 extend circumferentially around the sections 2 and 3 and receive the matrix 12.

The matrix 12 may be of one piece, extending transversely across-the tread portion of,

the mold, but it is preferred to form the matrix in ,two circumferential sections,. corre-' sponding to the mold sections2 and 3 as well as in segmental sections. Twelve or more of such sections'areat present used to; completethe tire tread surface, one set of matrices beng placed in the channel 10 and another set in the channel 11-.

, The inner side edges of the channels 10 and 11 are formed to provide definite shoulcanbe clearly seen in Figures 1 and 2 of the drawing thus eliminating the lisu'al clamping ring. These with meeting faces 19 which close the molding cavity between the sections 2 and 3 and tions.

- Heretofore,-in making molds havingthe matrix cast in sections, it has been the prac- 3 ties to cast the sectio'nsto the exact size det6 mained in t he'matrix on the next'castingopsired This has proved to be v unsatisfactory since the ends of the castings have slight roughn due to the molds in which they were made, and it has been impossible to prevent crevices be formed between the se arate matrix into which the rubber flowedw on under pressure. Since the rubber retively, forming complemental sides are also provided.

oration, rubber as built up until undesirable barnacles were formed which made it necber from the ]oints between the separate matrices,

I have found that b' making thematrix from any suitable me the excess metal at their edges to form tight scams or joints between the matrix sections trix is cast with an excess amount of metal on :each ed thereof, the edges destined to abut with t e edges of the other matrices beingalso provided with beads. The excess on the ends is shown by the dotted lines 16 and 17 and thebeads 16' and 17 After thesections are cast and thefins and gates'removed, the next operation is to ma- .chine the ends 16 and 17 'so that, when the individual matrices are brought together, a

fit as true as possible will be obtained. The

I n d b suchasaluminum or a uminum a 0y y making the castings over-size and machining and smoothing of machining; though it removes a portion of the excess metal, does not entirely remove the beads. Thus, at the end of this operation the individual matrices have smooth ends provided with u beads. The edge 1& isthen. mac ed 'to fit exactly to t e shoulders 13 of the mold sections 2 and 3. 1

The mold sections 2 and 3 are then heated to expand them and while so expanded the matr'ices are sli" ped into the channels 10 and 11 thereof. 7 Ugon and contraction of the mold sections, due to cooling, the mat No matter rices are locked firmly together. how true and exact the fit between the individual matrices is, there will usually be:

into the joints, whereby both the beads and joints are obliterated and no ri or ribs are produced on the tire. The 0 literation' of the joints and beads may be accom lished in various manners. I have obtain satismatrices to a burnishing operation after looking them in the mold. This operation also sharpens the design on the tread, whereby a more distinct'tread is produced on the tire- The flanges 14 of the matrices are then fas.'

tened securely to the-sections 2 and 3 by means of the screws or bolts 15. The mold sections.

are then placed in jigs and the'faces 19 of the flan -es'14: of the matrices 12 are machined and/or urnished. .This machining and/or rat,

burnishin also smooths any projecting tions of t 0 heads of the screws 15 so when the two sections 2 andB-arew bolted togather, a very close fit between the fla 14 10! the matrices is permitted, cnab the mold or ridges on the'tire, except what usually passes into the air vents formed by complemental grooves in the machined faces 19 of the flanges 1 4. The air passing through the vents 20 finds its further escape between the joint of the overlapping flanges 5 and 6 of the mold-sections.

In the manufacture of tires of this tygae, it 1g-.

I is customar to place the carcass 22 of are 1 of a tire in the mold, insert the rubber necessary to form the tread, place an air bag or inner tube 23 inside the tire, close the mold and subject the tire to the usual vulcanizing operation.- This causes the uncured rubber oi new one.

the tread'to first take the form of the matrix and then be vulcanized while remaining in the mold. This vulcanization is by heat. Owing tothe fact that the matrices are'made of aluminum or aluminum alloy, when the entire mold is heated the aluminum or alu'minum alloy having a greater coeflicient of 'expansion than thesteel tends to force the sections still tighter together, so that no groove is formed between the separate matr ces in .which rubber can be deposited. Whenever the matrix becomes injured in removing the tire from the mold, it is very simple to lmock out the injured section and replace it with a I have found that by the of aluminum or alloy thereof a very glossy surface is imparted to the face of the tire which makes it --'be understood that,

easier to remove the tire from the mold and revents the rubber of the tread from adhermg theretoi Heretofore, in the steel .molds formerl used onl forty or fifty tires could be cast fore it ecame necessary to sand-w blast the moldsbefore removing the rubber barnacles. By means of my invention four tofive times the number of tires may :be cast in m mold before it is necessary .to clean it, w ch is preferablydone bya blast of pumice,'rottenrock or the like, and even then the accumulation in the mold is materially less than under present practices and conditions. With other molds having the matrices made in sections it was customary to remove the matrices from the mold and clean them after nearlybevery molding operation.

In the a ve method the segments were disposed in a heat-e anded mold. It is tothough this method is preferable, the invention is not limited there-.

5 to since it is apparent that the segments may be disposed in the. mold without shrinking the mold. Thus, for example, the segments maybe ppsitio'ned in a cold mold, precautions ta en being to obtain as truea fit as possible. 'The sub uent burnishing treatment will obliterate t e joints and beads: operation due to thefact. that the ts have-a greater coeficient of expansion than the mold, the'heat of vulcanization will force the segments tighter together. I claim; i 1. A method of pre a molds for. tire casings and the likew ich mcludes expandra 'ty of segmental matrices edge to edge in circumferential relation with res mold cavity, then contracting the mold, whereby the adjacent abutting edges of' the matrices are brou ht into intimate contact.

.2. A method 0 pre aring molds for tire casings and the like w ich includes expanding a tire mold by heat, disposing in said expanded mold a plurality of segmental matrices having a greater coeflicient of-ex ansion than said mold, said matrices being isposed edge to edge in circumferential relation with respect to the mold cavity, and then allowing the mold to cool, whereby the'adjacent abuttingedges of the.matrices are brought into intimate contact.

3. A method of pre aring molds for tire casings and the like wh provide smooth edges to form a tightjoint with the edges; of the other matrices, arranging said matrices circumferentially and edge toedgewith respect to the molding cavity of said expanded mold to form an annulus, and then permitting the mold to contract after theannulus has been completed, whereby the opposingedges of the matrices arebrought' in close and intimate contact.

4. A methml of preparing molds for tire .casin and the like which mcl-udes milling the e ges of a plurality'of segmental matrix sections so that their edges will abut in close relation, arranging said matrices circumfer-. entially around the cavity of a heat-expanded -mold to complete an annulus and then perpect to the in 'a tire mold, disposing in said mold a pluich. includes expand- -m.g a tire mold, providing a plurality of diemitting' the mold to cool, w ereby the op-'- posing.edges of, the matrix sections are brought into close and intimate contact.

' 5. A method of preparing tire molds which includes shrinking into a tire mold edge to edge against tlietread. portion of the molding cavity thereof a plurality of matrix sections of greater coefiicientof expansion than'the-mold.

6. A method of preparing tire molds which includes heating a mold of a relatively low coeflicient of expansion-and disposing there in while expanded a plurality of matrices of a relativelyhigher coeflicient of expansion arranged edge to edge to provide'a circumferential lining therein, and then'permitting the mold to cool I after the said circular lining has been completed, whereby the abutting edges of an matrices are brought into intimate juxtaposition.

-7. A method of preparing molds for tire casings and the like which includes fixedly disposing in the sections of a split mold a plurality of segmental matrices adjacent the split edges of the mold so chat the matrix edges in each mold section maybe brought 7 in contacting relation, then smoothing said tions are secured together.

edges of the matrices in-the: respective mold sections so that they will form a tight seam when the mold sections are'secured together.

8. A method of preparing molds for'tires which includes fixedly disposing in each section of a split mold a plurality of segmental matrices circumferentlally therein with the edges of the matrices projecting beyond said split edges of the mold, then smoothing the projecting edges of the matrices so that they will form a tight seam when the mold secwhich includes disposing a plurality of segmental matrices in close abutting relation and circumferentially with respect to the molding cavity of a mold, said matrices having uptween said matrices.

said beads an standing beads, remov' e joints formed bestantially obliterating t 11. method .of preparing tire molds which includes disposing a plurality of segmental matrices in close abutting relation and circumferentially with respect to the molding cavity of a mold, said matrices having upstanding beads on their abutting ends, and burnishing the faces of said matrices whereby the beads and joints between said-matrices are substantially obliterated.

12. Amethod of preparin tiremoldswhich includes machining the en of a plurality of segmental matrices having excess metal and beads thereon to provide smooth edges to form tight joints with the edges of other matrices, arranging said matrices circumfere entially and edge to edge with respect to the molding cavity of a mold, and then burnishing the faces of said matrices whereby the; beads and joints are substantially obliterated.

13. A method of preparing molds for tire casings and the like whichincludes expanding a mold, machining the ends of a plurality of matrices havin excess metal and beads thereon to pro die smooth edges to form and edgetoedge in said mold, ermitting ,said-moldfto contract, and burmshin the faces of matrices to substantially ob iterate said beads and joints. d v

14. A method of preparing. tire molds which includes disposing a plurality of segmental matrices in close abutting relation and circumferentially with respect to th inolding cavity of a nold, said matrices ha ing upstanding beads forcing said beadsj into the joints or seams between said matrices, whereb said beads and joints are substantially obliterated.

15. A method of preparing. tire molds which includes disposing a plurality of segmental matrices in close abutting relation and circumferentially with respect to the molding cavity and smoothing the faces of said matrices, whereby the scams or joints between said matrices are substantially obliterated.

16. A method bf preparing tire molds which includes disposing a plurality of segmental matrices in close abutting relation and circumferentially with respect to the molding cavity'and forcing a small amount of the material of which the matrices are formed into the seams or joints between said matrices, whereby said seams or joints are substantially obliterated.

17. A-- method of preparing the molds which includes shrinking into a tire mold a plurality of segmental matrices in close abutting relation and circumferentially with respect to the molding cavity,said matrices having upstanding beads on thelr abutting ends, removing said beads and substantially oblitcrating the jointformed between said matrices.

In testimony whereof, I have aflixed my signature.

GEORGE W. BUNGAY. 

